Deep Back Flashcards
Development of Deep Back
- From Mesoderm germ layer
- Each somite differentiates into a sclerotome and myo-dermatome
- myotome region of myo-dermatome gives rise to myoblast cells (embryonic muscle cells) that form muscles of trunk
- Even though most myoblasts migrate away from specific myotome of origin, they maintain their original nerve supply
2 divisions of myotomes
- Epaxial (dorsal) division
- nerve supply is from the dorsal primary rami of spinal nerves
- Muslces deived from this division include deep extensor muscles of back
- Hypaxial (ventral) division
- nerve supply is from ventral primary rami
- Muscles derived from this division include:
- infrahyoid
- flexor muscles of vertebral column
- quadratus lumborum
Deep Back Muscle Development
- Originally have segmental arrangement, extending from one vertebrae to the the next
- as a group, these muscles extend from skull to pelves, covered by deep fascia
- fusion between adjacent segments will take place throughout developemnt to form larger muscle masses covering more than one segment
- Sequential splitting of muscles takes place later to form different superimposed layers
Characteristics of Deep Back
- entire vertebral column moves smoothly during flextion, extension, & rotation
- due to origin/insertion overlap
- many back muscles function to support body weight by extending the vertebral column
- Transverse & spinous processes of vertebrae provide attachment of muscles
- majority of deep back muscles have multiple insertions and origins
Innervation of Deep Back
- Intrinsic Back muslces are the only muscles of body to be innerated by dorsal primary rami
- usually cross more than one segment of vertebral column, & therefore innervated by more than one spinal cord level
Cause of Back Strains
- results from extensive extension and rotation
- microscopic tearing of muscle cells or ligaments
Intrinsic Muscles of the back
- Mainly involved with extension of spine
- span the entire back from skull to sacrum
- are grouped according to direction of muscle fibers and length of muscle bundles
Groups of Intrinsic Back
- Splenius group
- arise from posterior midline of back and proceed laterally & superiorly to insert
- Erector Spinae Group
- arise from posterior midline of back (more laterally) and run longitudinally
- Transversospinalis Group
- arise laterally but travel toward midline to insert
- Suboccipital Muscles
- Do not follow above pattern
- responsible for movement of head & neck only
Which intrinsic groups assist with head movements?
Splenius group & Suboccipital Muscles
Superficial Layer of Deep Back
All three subgroups of erector spinae and aplenius muscles
Intermidiate Layer of Deep Back
Two parts of transversospinalis (semispinalis & multifidus)
Deep Layer of Deep Back
Segmental muscles and suboccipital muscles
Splenius group characteristics
- most superficial intrinsic muscles on posterior neck
- “Splenius” = bandage-like structure
- muscle represents bandage wrapped around neck
- muscle fibers arise from midline and run superiorly and laterally
- Consists of 2 muscles:
- Splenius Capitis
- Splenisu Cervicis
Splenius Captiis
- Broad flat muscle of the neck
- Partly covered by Trap & SCM
- Upper & larger of 2 splenius muscles
- fibers proceed superiorlaterally from origin to attach to the skull
Splenius Cervicis
- Narrow muscle located below and parallel to splenius capitis
- Fibers extend superiorly and laterally
- No fibers attach to skull
Erector Spinae Group Characteristics
- Largest muscle mess of back
- Froms prominent bulge on either side of lower part of vertebral column b/t spinous processes and rib angles
- Chief extensor of vertebral column
Origin of Erector Spinae Group
- Very extensive common tendon of origin
- Attaches to:
- sacrum
- iliac crest
- spiinous process of lumbar and two thoracic vertebrae
Divisions of lumbar region of erector spinae group
- Ilioscostalis
- Longissimus
- Spinalis
These then further divide into three parts according to superior attachments
The muscle of each part is made up of overlapping short muscle fibers to provide smooth controlled action
Iliocastalis
- associated with ribs
- Divided into:
- ilicostalis lumborum
- ilicostalis thoracis
- ilicostalis cervicis
- Most lateral column of erector spinae group
- all three parts of this muscle have origin and/or insertion on ribs
Longissimus
- Associated with transverse processes of vertebrae
- Divided into:
- Longissimus thoracis (largest & lowest section)
- Longissimus cervicis
- Longissimus captiis
- Intermediate division
- Lower part of this muscle blends with ilicoastalis lumborum
Spinalis
- Most medial and smallest division of erector spinae
- poorly developed in most individuals
- When well developed, extends from thorax to skull
- contains thoracis, cervical, & lumbar segments
- Usuall only thoracic part present
- lies medially to longissimus thoracis
- extends from spinous processes of lumbar vert to spinous proceesses of upper thoracic vert
Actions of erector spinae group
- Bilaterally - extend the head and vertebral column
- Unilaterally - laterally flex the head and vert column
- Chief extensor of the vertebral column
Transversospinalis Muscle Group Characteristics
- Lie deeper to erector spinae group
- shorter than erector spinae
- slant inward from origin to insertion
- Originate from trnasvers processes and proceed to spinous processes of more superiosly located vertebrae
Muscle masses of Transversospinalis Muscle group
- Semispinalis
- Multifidus
- Segmental Muscles
Semispinalis
- Semispinalis thoracis
- semispinalis cervicis
- Semispinalis capitis
- Muscle fibers arranged longitudinally (like erector)
- Muscle fibers span over about 4-6 vertebrae
- lacking in lumbar region
- lie superficial to multifidus
Multifidus
- Deeper to semispinalis
- thickest in lumbar area
- present throughout back
- muscle fibers go from transvers to spinous processes
- individual segments don’t have names
- ends in cervical region
- different parts are not usually distinct
- sacral and lumbar areas of muscle are covered by erector spinae
- thoracic & cervical regions covered by semispinalis
- muscle fibers cover 2-4 vertebrae
Segmental Muscles
- Deepest part of transversoapinalis group
- better developed in cerivical and lumbar regions
- is deep to multifidus
- Three sets include:
- interspinalis
- intertransversarii
- rotators
Interspinalis
- Well developed in cervical and lumbar regions
- muscles are separated by interspinous ligaments
- stretch between adjacedn spinous processes from C2-T1
- Lacking in thoracic region
Intertransversarii
- Run vertically between adjacent transverse processes
- well developed in cervical and lumbar regions
- lacking in thoracic region
Rotatores
- Have a single origin and a single insertion unlik most other back muscles
- span 1 or 2 vertebrae
- best developed in thoracic region
- 2 sets:
- long rotatores (longus)
- found in lumbar, throacic and cerviceal
- skip vertebrae
- Short rotatores (brevis)
- found in lumber, cervical, and thoracic
- attach to vertebrae above (don’t skip)
- long rotatores (longus)
Suboccipital Muscles
- Group connects the skull to the atlas and axis
- Consist of:
- Oblique capitis inferior
- oblique capitis superior
- rectus capitis posterior major
- rectus capitis posterior minor
Suboccipital Triangle Muscles
Created by oblique capitis inferior, oblique capitis superior and rectus capitis poasterior major
Rectus capitis poasterior minor is part of traingle, but not a boundary
Blood supply to suboccipital muscles
- Vertebral artery originates at base of neck from subclavian
- passes through trnasverse froamina of cervical vertebrae
- enters suboccipital triangle trhough foramen magnum
Nerve supply to suboccipital muscles
dorsal ramus of C1 (suboccipital nerve)
Greater Occipital Nerve
- Dorsal ramus of C2
- emerges from below the oblique capitis inferior muscle (outside of the triangle)
- Corssses the muscle and travels obliquely across traingle to back of skull
- sensory nerve to posterior part of scalp
- does not provide innervation to any of the muscles in the triangle
Actions of Deep Back Muscles
- No individual discrete action for any of the deep
- muscles function together as large groups because the origins and insertions of the muscle fibers overlap
Movements of the Vertebral Column
- Flexion
- Extension
- Lateral Flexion (side to side)
- Rotation (same side or opposite side0
Flexion of Vert Column
- Anterior trunk muscles
- Gravity
- Back muscles act as antagonistic - relax gradually to produce smooth movement
Extension of Vert Column
- All deep back muscles exvept intertransversarii
- Erector spinae acts as chief extensor muscle
Lateral Flexion of Vert Column
- Intertransversarii
- Splenius captitis and cervicis rotate the head to the same side and laterally flex the neck
- erector spinae group initiates lateral flexion unilaterllly
- all muscles on opposide side control flection by gradually relaxing
Rotation of Vert Column
- Multifidi, Rotatores, and Semispinalis muscles rotate teh trunk to the opposite side
- Splenius muscles and Erector spinae extend trunk and help rotate it to the same side
Movements of Head
- Oblique capitis inferior and rectus capitis posterior major/minor rotate the atlas and turn face to the same side
- Oblique capitis superior and rectus capitis posterior major/minor extend the head bilaterally and flex it to the same side unilaterally
Which of the following muscles are dervied from the epaxial division?
Infrahyoid
Flexor muscles of back
deep extensor muscles of back
quadratis lumborum
Flexor muscles of back AND deep extensor muscles
Deep extensor muscles of back
The fibers of the following muscle/muscle groups proceed superiorly and medially
Erector spinae
Rotators
Transversospinalis
Splenius
Rotators and Trasnversospinalis
Rotators and transversospinalis
__________ muscles represents the lateral division of sacrospinalis
Iliocostalis
Longissimus capitis
Longissimus Cervicis
Spinalis
Iliocastalis
Which of the following muscles is/are attached at the mastoid process?
Splenius capitis
longissimus thoracis
longissimus capitis
Semispinalis capitis
Splenius capitis AND longissimus capitis
Splenius capitis AND longissimus capitis
